Acid-phosphate process



Arts

3 UNITED s'r PATENT OFFICE.

nnanrmT mmnrnns, or PITTSBURGH, rnrmsrnvanm, Assumes. Tumour. rnn. TILIZER wonxs, or cnrcneo, rumors, A CORPORATION or n'nw-Jnasnr.

ACID-PHOSPHATE rnocnss.

1T0 Drawing.

To all whom it may concern:

Be it known that I, HERBERT H. Mums, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and 6 State of'Pennsylvania, have invented certain new and useful Improvements in Acid- Phosphate Processes, of which the followin is a specification. I e present invention relates to the pro- 10 duction of acid phosphate, particularly, but not necessarily restrictedly, for. use as a fertilizer.

The leading aim and prime purpose of the invention is the provision of a method 18 or process whereby theacid phosphate may be made at materlally less expense than by the present method.

In the customary process of making such acid phosphate, the phosphate-rock is 20 ground dry and is then treated with sulphuric acid of the proper strength, the product being deposited in a den where it is which, after such setting, it is removed.

One feature of my improved process re.- sides in the wet grinding of the rock, which results in economy-of operation because the power required for wet grinding is less than half as much as that needed for dry grinding, or stated somewhat difierently, the output. of a I wet grind1ng,..with the furtherv advantage that a type of mill may be used for wet 'grindin' for which the upkee costs are a5 materia y less than on the usua mills used for 'nding of plios hate-rock. Y Vdl n pliosphatewrock i ground wet about 40% of 1ts weight of water must be used, and if a slurry consisting of such a mixture 40 were acidulated by the ordinary method in a mixer, even with 60 B. acid, the mass would not'set properl in the den, and when recovered from tne en would be too wet for use. It would have to be dried. Under these conditions, it would be equivalent to acidulating rock with from 40-'B. to .45 B. acid, and the weakest acid that can be successfully used for ordinary acidulation is B.

m It would not be feasible to use stronger than B. acid for adding to the' wet rock, since 60 B. acid is the strongest it ispossibleto produce byythe lead-chamber process without a concentration 0 ration,

3 and to concentrate the ;acid woul', far

ermitted to set or harden and from given mill is-much increased by of the mixture is are 45 B., is used the'mixtureis Application filed December 21, 1922. Serial m5, 608,852.

too expensive, just as a subsequent handling and drying. of the acid phosphate-would be.

Furthermore, when Wet rock is acidulated in a mixer, it has a tendency to ball, that is, form smallnodules whichareunacted upon in the interior. These are dropped into the den, wherethey lie dormant, and the result is'that the acid phosphate produced contains small kernels of' material with a comparatively high percentage of insoluble hosphate. 1

The sudsequent step in the new process rock to a direct heat dryin method which permits the useof the initia or preliminary wet grinding, and any balls tending to form are disintegrated by the -motion of the charge through thedrier and the appli--' cation of heat which causes the moisture in the interior of the balls to vaporize and ound with. from is subjecting the wet-ground and acidulated I 33% to 40% of its weig t of water in a-- u tube or other suitable mill, and the slurry from the mill is run to a mixer where the. proper amount of 60 B. sulphuric acid is added to it.

The exact amount of acid to be used depends in large measure upon the ty e of rock being acidulated, or exampl if Tennessee rock, analyzing about trical-- cium phosphate were used, approximately 78 pounds of 60 B6. acid would be required for each pounds of rock. a

The quantity of water present in the rock slurry issuchthat the acid, when added, is diluted to between 40 and 45 B., whereas according to the old process the usual strength of acid used for acidulating is between 50 and 55" B. When this latter strength of acid is used the setting 1 rapid, but when a slightly more-dilute acid, such as 40 B6. or 1 what longer, permitting it to ow easily to a drier after thorough mixing. l Therefore,- the mixture of rock and acid is allowed. to flow continuously-from the the inclined cylindrical rotarytype w h is wellknownr 2 Q 1 liguid someor to a direct-heat drier, preferabl 0! drier or, kiln, it becomes well broken up or disintegrated due to the rotary motion of the kiln and the action of the drag-chain or scrapers.

This action assures uniformity of the product in respect to the chemical condition and produces a well aerated article of good mechanical condition.

The product as discharged from the kiln is conveyed'to the storage pile. The direct-heat rotary drier is preferable for thisprocess, because it is simple in construction and operation and has no compli-v gated moving mechanism on its interior i which is dificult to operate and to'repair.

The interior of the rotary drier is easily accessible and'the charge is very readily prevented from building up or sticking to its interior.

The advantages of this new process may be summarized as follows:

The rock may be ground wet, whereas in the usual den system, the rock must be ground dry in order to obtain satisfactory results on acidulation. Wet grinding is much cheaper than dry grinding, probably not half as expensive.

The initial investment for, a -lant of this type is materially less than t at required for a den system of equal capacity.

The process is continuous and not an intermittent one.

ical condition without fur her treatment.

The heatdn the drier assists in hastening the chemical reactions which in turn are exothermic, and, therefore, aid in the drying. The process, therefore, is much more re 'd than the usual one. p e slight excess of water used in wet grindingassures ease of handling and uniormity df condition of the charge entering the dr1er, and, further, it prevents the denger of overheating the product by assuring an atmosphere of ,steamat all times inthe ll; c

p e productgis equal in every respect to ordinarily acid phos hate and costs substantia y less to pro uce.

.6 1 The cost of the fuel fordryingis a very' of the provid ed with a'drag- As the material moves down through the Thproduct is in good 'hysical and chemessence small item and it is oilset many times by the various savings. introduced.

It will be readily understood by those skilled in the art that thenew process is not limited and restricted to the precise andexact details presented because these may be modified within comparatively wide limits without departure from the heart and essence of the invention and without the sacrifice of any of its substantial benefits and advantages.

It may be noted in passing, that with dry grinding of phosphate rock, it is first necessary to dry the rock at an ap reciable expense, whereas, when wet gr ingis racticed, the initial dry' g is not require and the cost of such drying saved I claim: 1. The process of producing phate, consistin' in wet" grindmg the phosphate-rock, aci ulating such wet round acid phos rock, and heating and drying said aci ulated 7 a rock at a temperature to produce available acid hosphate as a roduct. -2. e process o producing acid .phate, consisting in hosated providingl acid ground phosphate-roe and eating and rying such acidulated rock at a temperature to produce available acid phosphate as a product, y

3.. The process of producing acid hosphate, consisting in providing acid ated ground-rock -and heating and drying such acidulated rock during agitation of the latter at a temperatiire to produce available acid hosphate as a product.

4. e process of producing acid phosphate, consisting in wet grinding the phos- ,phate-rock with about 33% to 4.0% of its weight by water, adding to the slurry'thus formed approximately 78 pounds of around 60 B. s hurio acid for each 100 ounds of rock, an heating and drying suc acid slurry, while conveying and agitating the ,same, by combustion gases traveling concurrently with the charge until the product contains about 16% moisture.

phate, consistingfin wet phate-rock, adding to sue slurry about 60 B. sulphuric acid until the acid slurry is of about 40 to45 Be, and heating and dry- 5. The process of producing acid phos- I inding the phosing such. acid slurry, while agitating and conveying the, same, until theiproduct contains about 10% moisture. p

' 6. The process of producing acid phosphate, consisting in wet grinding the phoshate-rock, adding to such'slurry about 60 6. sulphuric acid until the acid sl urry is of about 40 to 45 Be, and heatingand drying such acid slurry.

The process of producing acid phos 'phate, consisting in wet inding the phoshate-rock, addm to sue slurry about 60 sulphuric aci until the acid slurry is of about 40 to 45 Be., and heating and drying such acid slurry while agitating and conveying the same.

8. The process of producing acid phosphate, consisting in wet grinding the phosphate-rock, adding sulphuric acid to the slurry, and heating and drying such slurry in contact with hot combustion gases while agitating and conveying the slurry and at a temperature to produce available acid phosphate as a product.

9. The process of producing acid phosphate, consisting in wet grinding the phosphate-rock, adding sulphuric acid to the slurry, and heatin and drying such acid slurry in contact with hot combustion gases whilefagitating and conveying the slurry HERBERT H. MEYERS. [L.s.] I 

